Process for the catalytic hydrogenation of hydrocarbons for the production of high-viscosity-index lubricating oils

ABSTRACT

A novel two-stage hydrogenation process for producing lubricating oils is disclosed which comprises passing a deasphalted vacuum residue and/or vacuum distillate feedstock through a preheater, contacting the resulting feedstock with a catalyst consisting of sulfides and/or oxides of the VI and VIII group metals on a slightly acid support in the presence of hydrogen at certain temperature, pressure, space velocity and hydrogen flow conditions (first stage), contacting the resulting product under the same temperature, pressure, space velocity and hydrogen flow conditions as in the first stage with a catalyst consisting of sulfides and/or oxides of the VI and VIII group metals on an acid support, conveying the resulting products to a high-pressure separator where hydrogen is removed, purified and recycled, conveying the resulting product to a low-pressure separator where undesirable gases are removed, introducing the resulting product into a stripping column, where certain useful byproducts are removed, transferring the bottom products to a deparaffination unit wherein paraffins removed therein are recycled to the first reaction stage and then conveying the deparaffinated product to a vacuum-fractionating column where the desired lubricating oils are obtained.

United States Patent Girotti et al.

[ Feb. 15,1972

[54] PROCESS FOR THE CATALYTIC HYDROGENATION OF HYDROCARBONS FOR THEPRODUCTION OF HIGH-VISCOSITY- INDEX LUBRICATING OILS [72] inventors:Pierleona Girotti; Telemaeo Floris, both of Donato Milanese; GiancarloPecci,

Milano, all of ltaly 73 Assignee: Snam Progetti S.p.A., Milan, Italy[22] Filed: Feb. 14, 1969 [21] Appl. No.: 799,341

[30] Foreign Application Priority Data Feb. 14, 1968 Italy ..12716 A168[52] US. Cl. ..208/89, 208/143, 208/254 H [51] Int. Cl. ..Clg 23/00 [58]FieldofSearch ..208/l43,212, 89,58, 59,61, 208/72, 104

[56] References Cited UNITED STATES PATENTS Duir et al ..208/89 Watkins..208/59 [57] ABSTRACT A novel two-stage hydrogenation process forproducing lubricating oils is disclosed which comprises passing adeasphalted vacuum residue and/or vacuum distillate feedstock through apreheater, contacting the resulting feedstock with a catalyst consistingof sulfides and/or oxides of the Vl and VIII group metals on a slightlyacid support in the presence of hydrogen at certain temperature,pressure, space velocity and hydrogen flow conditions (first stage),contacting the resulting product under the same temperature, pressure,space velocity and hydrogen flow conditions as in the first stage with acatalyst consisting of sulfides and/or oxides of the VI and VIII groupmetals on an acid support, conveying the resulting products to ahigh-pressure separator where hydrogen is removed, purified andrecycled, conveying the resulting product to a low-pressure separatorwhere undesirable gases are removed, introducing the resulting productinto a stripping column, where certain useful byproducts are removed,transferring the bottom products to a deparafilnation unit whereinparafiins removed therein are recycled to the first reactionstage andthen conveying the deparaffinated product to a vacuum-fractionatingcolumn where the desired lubricating oils are obtained.

Claims, 3 Drawing Figures PATENTEDFE'B 15 ran sum 2 0F 3 FIG. 2

PROCESS FOR THE CATALYTIC HYDROGENATION OF I-IYDROCARBONS FOR THEPRODUCTION OF HIGH- VISCOSITY-INDEX LUBRICATING OILS This inventionrelates to a process for the catalytic hydrogenation of hydrocarbonfeedstocks and in particular to the production of high viscosity indexlubricating oils. It is known that lubricating oils are obtained fromhydrocarbons by extraction with a selective solvent such as phenol. Alsowell known are catalytic hydrogenation processes that make it possibleto get said lubricating oils from high-boiling feedstocks fractions asfor instance in the process described in U.S. Pat. No. 2,554,281 where acatalyst, consisting of one or more sulphides of VI and VIII groupmetals of the periodic system, is employed for said hydrogenation.

It has now been found that high viscosity index oils may be prepared bymeans of a particular process of catalytic hydrogenation of deasphaltedpetroleum feedstocks and/or of vacuum distillates and .that such aprocess also makes it possible also to obtain both higher yields and theproduction of other products such as jet fuels and high-qualityfeedstocks for catalytic reforming.

Particularly it has been observed that better results are achieved if inthe aforementioned process the catalytic hydrogenation zone is dividedin two stages each one of them utilizing different catalytic systems andsuitable operative conditions.

In the first of the above-cited stages the following basic reactionsoccur: desulfurization, denitrification, of partial hydrogenationpolycyclic aromatics, carbon residue reduction.

The operative conditions are regulated in such a wayvto eliminatecracking reactions as much as possible.

In the second stage the following basic reactions occur: completion ofthe hydrogenation reaction of the' polycyclic aromatic hydrocarbons,selective splitting of the polycyclic naphthenic compounds to yieldlower naphthenes comprising side-branched paraffin radicals, linearparaffins isomerization, selective hydrocracking for low-boilingisoparaffins.

In the first stage the catalyst comprises oxides and or sulphides of VIand of VIII group metals of the periodic system carried on a slightlyacid support as alumina.

In the second stage the oxides and or the sulphides of the metals of VIand VIII group have an acid support as for instance silica-alumina.

The preferred feedstocks are. the following: deasphalted residue and/orvacuum distillate of any source and limitless as far as the sulphur andthe nitrogen content is concerned. The ratio between the deasphaltedvacuum residue and the vacuum distillate will be selected and a functionof the type and the quality of the desired products.

On the whole, for the production of oils with a viscosit index of about100 it is possible to start preferably from a mixture of deasphaltedvacuum residue and vacuum distillate, while for the production ofmultigrade lubricating oils preferably may be used a deasphalted vacuumresidue alone or occasionally with the addition of vacuum distillate.

With the process according to the present invention it is possible toobtain lubricating oils having viscosity indexes ranging between 90 and145 by varying the operative conditions, the characteristics of thefeedstocks and the ratio of the contact time in the two stages.

Depending on the selected feedstocks and operative conditions thefollowing byproducts are obtained in variable amounts:

1. motor gas oil with an high Diesel Index and a very low pouring point;

2. Jet fuels with high qualitative characteristics as a low content ofaromatics and a very low pouring point;

3. Naphtha for reforming feedstocks with an high naphthenic content,particularly suitable for producing aromatics as toluene and xylenes;

4. Light lubricating oils to be used for instance as hydraulic oils; 5.Very good paraffins. The use of a first stage, where a catalyst with thecharacteristics described before is employed, allows better workingconditions in the second stage since on the catalyst of said secondstage arrives a denitrated, desulfurized and partially I hydrogenatedfeedstock and therefore more suitable to be subjected to the followingsteps.

Moreover, since the majority of the exothermic reactions occur in thefirst stage the catalyst of the second stage is subjected to a lesserthermal shock, this fact being a positive factor for a betterselectivity in the typical reactions of this stage. The application ofthe two stages, each one having a welldefined activity allows one toadjust the catalytic system to feedstocks with different characteristicsby varying, suitably, as aforesaid, both the operative conditions andthe amounts of the two different catalysts.

An example of the process comprises the following steps: hydrogenatingtreatment in two stages, as said before, stripping, deparaffination andvacuum distillation.

In the hydrogenating treatment the flow course with respect to thereactor may be both upward and downward, the two stages having thepossibility to be comprised either in a single reactor or in tworeactors or in more reactors arranged in series.

The deparaffination may be carried out according to any one of theconventional method as for instance by means of the formation of adductswith urea or by means of solvents as propane, methyl ethyl-ketone a.s.o.

In the reaction zone besides the recycle of the necessary hydrogen, arecycle of products may be provided substantially with the purpose tocontrol in a better way the thermal phenomena. The paraffin coming outfrom the deparaffination unit may be introduced again in the processcycle.

The upward flow of the feed in place of the downward one is preferablebecause it makes it possible to work at a lower temperature when thespace velocity is equal and at a higher space velocity when is equal tothe temperature. On the other hand it has been observed that with anupward flow major selectivity is obtained, namely a higher yield with anequal viscosity index.

The possibility of working independently in each one of the two stageseither under the same operative conditions or under different onesallows, as already reported before, to obtain results otherwiseimpossible to achieve. I

The operative conditions of both stages are comprised between thefollowing values: temperature ranging between 350 and 450 C., pressureranging between 50 and 500 kg./cm. space velocity ranging between 0.1and 5 v./v./hr. The l-I introduced with respect to 1 liter of feedstockbeing l502,000 N l/l.

In FIG. 3 is reported with an illustrative purpose, but withoutintention to limit this invention, an outline of the process. Thefeedstock by means of line I, together with the hydrogen of the recycleand with the one which enters through 2 and which is necessary tocomplete the l-l lfeedstock ratio, is sent to a preheater 3, thenthrough 4 enters from the bottom into the system of reaction andprecisely into the first stage 5 where it meets the catalyst carried onthe aforementioned slightly acid support, then the products flow bymeans of conduit 6, and always from the bottom, into the second stage ofreaction 7 containing the catalyst with an acid support where thehydrogenation reactions are completed.

The products through 8 are transferred into a high-pressure separator 9and therefrom via line 10 the hydrogen is separated which afterdepuration is recycled to the reaction zone.

The reaction product is conveyed through conduit 11 into-a low-pressureseparator 12 wherefrom undesirable gases are partially removed, thensaid reaction product is introduced into a stripping column 14 via line14, in said stripping column are removed gas, gasoline and gasoil,having the last two products, or according to the case only one of them,the possihility of being recycled to the reaction zone through line 19and line I.

The bottom product is passed from stripping column, via line 15, to thedeparaffination unit 16 wherein paraffin is removed either by means ofmethyl-ethyl-ketone or according to different known technics.

From 16 a part or the whole paraffin is recycled to the reactor throughlines 20 and 1. The deparaffinated product is forwarded via line 17 tothe vacuum-fractionating column 18, wherein are obtained, as overheadproduct, a light lubricating oil and from the medium fractions and thebottom ones the wished lubricating oils.

The invention will be more clearly illustrated by the following examplesas far as its advantages and its meaning are concerned.

EXAMPLE I With the purpose to evaluate the difference existing between aprocess with a single stage and a process with two stages comparativetests have been carried out with a feedstock constituted by adeasphalted Kuwait residue having the following characteristics:

Specific gravity at IS C. 09353 Viscosity at 37.8 C. cSt 762 Viscosityat 989 C. cSt 35.72 Viscosity Index (ASTM D 567) 84.1 Sulfur percent byweight 3.12 Pouring point temperature in C. +43

TABLE I Feedstock: Kuwait deasphaltegl vacuum residue with est.viscosity at 8.9=35.72

Process with Single stage Two Stages Tests A B A;

Operative conditions:

Pressure kg/cm. 200 200 200 Temperature, C 400 410 390 Space velocity,v./v./h 0.5 0.6 0.5 R0 cle oi HzN, l.ll 840 840 840 840 Charaet ristiesof the 385+ fraction:

45 64. 3 57. 2 0. 8753 0. 8782 0. 8642 91. 90 140. 4 88. 30 Viscosity at98.9 C. est.-. 20 10. 92 13. 89 10. 59 Viscosity index (AS'IM D-567).99. 5 111 103.1 110. 7 Pouring point temperature C.) 2 10 -13 -10Characteristics of:

(a) Gasoil 180-350 fraction:

Diesel index 60 65 Pouring point temperature, C 50 50 (b) Kerosene150-250 fraction:

Smoke point 30 33 Freezing point C. -65 65 (c) Gasoline C1 (180 0.):

N aphthenes, percent by volume 62 Aromatics, percent by volume Thecatalysts employed in the two stages process consisted in the firststage of nickel-molybdenum sulphides supported on alumina and in thesecond stage nickel-tungsten sulfides on silica-alumina and in thesingle stage process nickel and tungsten sulphides on silica-alumina.

The operative conditions employed were:

Pressure 200 kgJcm. Temperature .anging from 300 up to 410 C. Spacevelocity 05 v./vi/h.

Hydrogen flow 843N l./l. of feedstock The hydrogenated product comingout from the low-pressure separator was fractionated into one fractionranging from the initial point up to 385 C. and another one havingboiling point higher than 385 C. (385+C.).

The characteristics and the percent by volume yields of the fraction385+C. deparafi'mated at l7.8 C. are reported in Table l andcomparatively in the graph of FIG. 1 wherein the influence of the firststage on the selectivity of the hydrogenation process according to thepresent invention is pointed out.

The feedstock was a Kuwait deasphalted vacuum residue.

On the ordinates were plotted the viscosity indexes and on the abscissasthe yield of the lubricant bases as percent by volume with respect tothe feedstock.

The straight line nearest the axis of the abscissas is referred to aprocess with a single stage, while the one having ordinates with highervalues is referred to the process having both the first and secondstage.

EXAMPLE 2 Pressure Hydrogen flow 200 kgJcm. 843 N l./l. of feedstock Theincrements of temperature, required for obtaining a fraction having aboiling point higher than 385 C., deparaffinated at l7.8 C. and with aconstant viscosity index in function of the catalyst life, given asvolume of feedstock for yolume of catalyst, are reported for both casesin Table 2.

TABLE 2 Increment of temperature required for maintaining constant theviscosity index of the oil bases produced. The feedstock was always theone cited in the Example 1.

Catalyst lite Single stage process, Feedstock vol/catalyst vol. T., 0.

EXAMPLE 3 The operative conditions employed were in both cases thefollowing:

Pressure kgJcm.

Temperature 410 C.

from 0.25 up to 0.5 v./v./h. 843 N l./l. of feedstock Space velocityranging Hydrogen flow The hydrogenated product coming out from thelow-pressure separator was fractionated into two fractions the firstranging from the 1?. (initial point) up to 385 C. and the second onehaving a boiling point higher than 385 C.

The yields in percent by volume, in function of the viscosity index ofthe deparaffinated fraction having a boiling point higher than 385 C.,were plotted in the graph of PK}. 2, wherein is pointed out theinfluence of the flow diagram on the hydrogenation process selectivityaccording to this invention. The feedstock was the same mentioned in theExample 1. On the ordinates are plotted the viscosity indexes, while onthe abscissas axis are plotted the yield of the lubricating bases givenas percent by volume with respect to the feedstock.

The dashed straight line refers to the process having a downward flow ofthe feedstock and the continuous straight line refers to the processwith an upward flow of the feedstock.

What is claimed is:

1. Process for the production of mixtures of lubricating oils withviscosity index ranging between and 145, motor gas oils with a highDiesel Index and a very low pouring point, jet fuels with a low contentof aromatics and very low pouring point, naphtha suitable for reformingfeed at high naphthenic content, light lubricating oils and paraffins,which comprises introducing a deasphalted vacuum residue and/or vacuumdistillate together with hydrogen, after initial passage through apreheater into a first stage-of reaction which contains a catalystcomprising sulphides and/or oxides of a Group Vl metal and a Group VIIImetal of the periodic system on alumina support at a temperature of 350to 450 C., at a pressure of 50-500 kgJcm. with a space velocity rangingfrom 0.1 up

- to 5 with a hydrogen flow of ISO-2,000 N 1/ l of feedstock,

system on silica-alumina support, under temperature, pres sure, spacevelocity and hydrogen flow conditions which are the same as in the firststage, passing the products coming out from the second reaction zoneinto a high-pressure separator for separating hydrogen, passing thereaction product into a low-pressure separator to separate gaseousimpurities and low-boiling paraffins, introducing the reaction productfrom said low-pressure separator into a stripping column to removegasoline, jet fuel and gasoil passing the bottom product from saidstripping column to a deparaffination unit to solvent extract waxyparaffins, and the deparaffinated product is sent to avacuum-fractionating column to obtain said lubricating oil products.

2. Process according to claim 1 characterized in that the feedstock andthe hydrogen flow in the reaction stages are upward.

3. Process according to claim 1 characterized in that the hydrogen andthe feedstock flow in the reaction stages are downward.

4. Process according to claim 1, characterized in that both reactionstages are provided in a single reactor.

5. Process according to claim -1 characterized in that the two reactionstages are provided in two reactors arranged in series.

6. Process according to claim 1 wherein said deasphalted vacuum residueand/or vacuum distillate contain nitrogen and/or sulfur.

7. Process according to claim 1 wherein said first-stage catalyst is amixture of nickel and molybdenum sulfides on an alumina support.

8. Process according to claim 1 wherein said second-stage catalyst is amixture of nickel and tungsten sulfides on a silicaaluminasupport.

9. Process accordmg to claim 1 wherem the hydrogen removed from thehigh-pressure separator is recycled to the first reaction stage afterpurification.

10. Process according to claim 1, wherein waxy paraffins removed fromsaid deparaffination unit are recycled to said first reaction stage.

2. Process according to claim 1 characterized in that the feedstock andthe hydrogen flow in the reaction stages are upward.
 3. Processaccording to claim 1 characterized in that the hydrogen and thefeedstock flow in the reaction stages are downward.
 4. Process accordingto claim 1, characterized in that both reaction stages are provided in asingle reactor.
 5. Process according to claim 1 characterized in thatthe two reaction stages are provided in two reactors arranged in series.6. Process according to claim 1 wherein said deasphalted vacuum residueand/or vacuum distillate contain nitrogen and/or sulfur.
 7. Processaccording to claim 1 wherein said first-stage catalyst is a mixture ofnickel and molybdenum sulfides on an alumina support.
 8. Processaccording to claim 1 wherein said second-stage catalyst is a mixture ofnickel and tungsten sulfides on a silica-alumina support.
 9. Processaccording to claim 1 wherein the hydrogen removed from the high-pressureseparator is recycled to the first reaction stage after purification.10. Process according to claim 1, wherein waxy paraffins removed fromsaid deparaffination unit are recycled to said first reaction stage.